WASHINGTON — President Barack Obama does not plan to announce his choice for attorney general before the November elections, shielding the nomination from the rough-and-tumble of midterm election politics. Delaying an announcement of a replacement for outgoing Attorney General Eric Holder, however, will set up a likely showdown with a lame duck Senate late this year on a compressed timetable. Senate Democrats have asked Obama to wait so controversy doesn’t arise over whether they will support a specific …